Macquarie Harbour (201494)
Australia, Australasia
Site overview
KBA status: confirmed
Global KBA criteria: A1a, A1e, B1
Year of last assessment: 2024
National site name: Macquarie Harbour
Central coordinates: Latitude: -42.3096, Longitude: 145.3851
System: marine
Protected area coverage (%): 67.74
KBA classification: Global
Legacy site: No
Site details
Site description: Macquarie Harbour is a large and ecologically significant estuary located on the south-west coast of Tasmania, Australia. It is the second-largest natural harbour in Australia, and is a deep, sheltered inlet covering an area of 276 km2. It is 35 km in length and 9 km across. Most of the harbour is relatively shallow, but it is up to 50 metres deep in some places.
It is part of the larger Tasmanian Wilderness World Heritage Area, and is bordered by the Franklin-Gordon Wild Rivers National Park to the south and the Tasmanian Wilderness World Heritage Area to the west. It is fed by a number of wilderness rivers, including the Gordon and King Rivers, and connects to the Southern Ocean through the narrow and very shallow (~5 m) entrance at Hell's Gates, a notorious, dangerous passage for ships.
Rationale for qualifying as KBA: Macquarie Harbour in south-western Tasmania, Australia, is the only remaining known locality for the Maugean Skate (Zearaja maugeana), which is the world’s only estuarine skate (Grant et al. 2019), and is presently considered one of the most geographically restricted and threatened elasmobranch (sharks and rays) in the world.
On the Red List of Threatened Species this species is listed as Endangered under criteria B1ab(i,ii,iii,iv)+2ab(i,ii,iii,iv) (Last et al. 2016). This assessment was completed in February 2015 and was published on the IUCN Red List in 2016 and is due to be updated byt the Specialist Group in 2025. The species is also included in The Action Plan for Australian Sharks and Rays 2021 (Kyne et al. 2021) which lists the major threats as increasing pressures from salmon aquaculture and pollution as well as being caught by recreational and commercial gillnetting.
The most recent Conservation Advice for the Maugean Skate portrays a species on a rapid trajectory to extinction if the degradation of its habitat is not halted (Australian Government 2023). As the last remaining site for the highly threatened Maugean Skate, Macquarie Harbour qualifies as an Alliance for Zero Extinction site as well as triggers KBA status under criteria A1a, A1e and B1.
Additional biodiversity: The physicochemical characteristics of Macquarie Harbour create a strongly stratified system with tannin-stained freshwater surface followed by brackish and deeper marine water. The rich tannin layers limits light transmission and acts as a thermal insulator for deeper harbour waters. In short, these characteristics enable Macquarie Harbour to mimic deep-sea conditions such that whitespotted dogfish (Squalus acanthias) reside in the harbour despite being typically found in coastal and oceanic habitats. Other elasmobranchs found in Macquarie Harbour that prefer similar coastal and deep-sea habitats include the Melbourne skate (Spiniraja whitleyi) and Thornback skate (Dentiraja lemprieri).
Manageability of the site: This site is solely managed by the Tasmanian government, mainly by Tasmanian Parks and Wildlife Service and the Department of Natural Resources and Environment Tasmania.
Supersedes another site: There are no existing KBAs in Macquarie Harbour.
Delineation rationale: The entirety of the marine environment of Macquarie Harbour is included in this proposal. The boundary was delineated using Australian Statistical Geography Standard Edition 3 States and Territories - 2021 https://www.abs.gov.au/statistics/standards/australian-statistical-geography-standard-asgs-edition-3/jul2021-jun2026/access-and-downloads/digital-boundary-files
The harbour's entrance, and the estuaries of the of Gordon River and King River were delineated using straight lines between the narrowest points, in order to form a continuous boundary (polygon) around the harbour.
The proposed Macquarie Harbour KBA is surrounded by the North-west Tasmanian Coast KBA. This is a legacy IBA that is triggered by a number of Least Concern and Near Threatened bird species. Since being recognised as an Important Bird Area in 2009 it has not been reassessed against the KBA criteria. These coastal regions are not managed together with the Macquarie Harbour marine environment, and hence it is not appropriate to consider expanding the North-west Tasmanian Coast KBA to include the proposed Macquarie Harbour KBA.
Habitats
Summary of habitats in KBA: The environment in Macquarie Harbour is highly stratified into freshwater, estuarine, and marine layers (Ross et al. 2022). Surface freshwater loading flows from the Gordon and King rivers, which characteristically has a high tannin loading, is warmer, and carries higher levels of dissolved oxygen. The estuarine layer has two stratifications; an upper layer that is high in dissolved oxygen where the Meaugean Skate primarily occurs, and a lower layer that is low in dissolved oxygen where the Maugean Skate transiently occurs (15-30 m depth). Marine water forms the bottom layer, which is driven into the harbour through the shallow Hell’s Gate inlet by tidal and wind driven forces. Factors that affect the quality and extent of the habitable shallow estuarine layer of the Maugean Skate include the volume of freshwater flow (top down compression) and marine infiltration which is driven by tidal and wind forces entering through Hells Gate Inlet (bottom-up compression) (Moreno et al. 2020).
IUCN Habitat | Coverage % | Habitat detail |
---|---|---|
Marine Coastal/Supratidal | 100 |
Threats
Summary of threats to biodiversity at KBA: Salmon farming is currently the most significant threat to Macquarie Harbour, in particular organic matter pollution from the farms and the associated reduction in dissolved oxygen concentrations. The water quality is also being impacted by hydroelectric dams in the main rivers feeding the harbour, as well as climate change, and historical mining pollution.
Salmon farming began in Macquarie Harbour in the late 1980s. After 2007 the industry steadily increased in size and peaked in 2014/15. An expansion of the lease area from 564 to 936 ha was approved in 2012 allowing production to increase from 20,000 tonnes to ~29,000 tonnes. In early 2017 the water quality had deteriorated to a point that there was substantial mortality of salmon in the farm and the allowable production was reduced. As of May 2020, the limits for salmon biomass in Macquarie Harbour are 9,500 tonnes. Between 1993 and 2009, relatively stable dissolved oxygen concentrations were recorded across Macquarie Harbour (MHDOWG 2014). Dissolved oxygen concentrations steadily decreased between 2009-2014, including within the Tasmanian Wilderness Heritage Area. In the deeper waters dissolved oxygen concentrations reduced from > 40% saturation to 10–20% saturation in depths >15 m (Ross et al. 2022). Since 2014, dissolved oxygen concentrations have varied seasonally but have not returned to pre-disturbance levels (EPA 2022; Ross et al. 2022).
Macquarie Harbour’s water quality is impacted by hydroelectric dams in the Gordon River and King River, both of which are tributaries. The impacts of climate change have resulted in the mean water temperate within the bottom waters of the harbour increasing 1.5-2°C between 1993-2020 (Ross et al. 2022), and climate modelling predicts that rainfall patterns will be altered (Grose et al. 2010). Mount Lyell copper mine upstream in the King River catchment was established in the 1890s, and while it closed in 1994, it has dumped over 100 million cubic metres of mine tailings, smelter slag, and topsoil into the harbour. The amount of pollution is decreasing over time but at a very slow rate.
Threat level 1 | Threat level 2 | Threat level 3 | Timing |
---|---|---|---|
Agriculture & aquaculture | Marine & freshwater aquaculture | Industrial aquaculture | Ongoing |
Climate change & severe weather | Habitat shifting & alteration | Ongoing | |
Energy production & mining | Mining & quarrying | Ongoing | |
Biological resource use | Fishing & harvesting aquatic resources | Unintentional effects: subsistence/small scale (species being assessed is not the target) [harvest] | Ongoing |
Additional information
References: Australian Government. 2022. Threatened species action plan 2022–2032. Department of Agriculture, Water and the Environment. https://www.dcceew.gov.au/environment/biodiversity/threatened/publications/action-plan-2022-2032.
Australian Government. 2023. Conservation advice for Zearaja maugeanensis (Maugean skate). Department of Climate Change, Energy, the Environment and Water. file:///C:/Janice/Rewild/Australia/Tasmania/Maugean%20skate/Maugean%20skate%20Conservation%20Advice%20Sept%202023.pdf
EPA (Environment Protection Authority Tasmania). 2022. Statement of Reasons for TPDNO Determination and Apportionment in Macquarie Harbour, 31 August 2022. https://epa.tas.gov.au/documents/Statement%20of%20Reasons%20- %20TPDNO%20Determination%20%201%20September%202022%20to%2031%20August%202027.pd
Fisheries Research and Development Corporation. 2023. Australian Shark and Ray Report Card. Published October 2023. https://www.fish.gov.au/docs/SharkReport/2023_FRDC_Zearaja_maugeana_Final.pdf
Grant, M.I., Moreno, D., Semmens, J. and Simpfendorfer, C. 2023. Population viability analysis of the Maugean skate Zearaja maugeana. Report prepared for the Australian Government Department of Climate Change, Energy, the Environment and Water, pp 40.
Grose, M.R., Barnes-Keoghan, I., Corney, S.P., White, C.J., Holz, G.K., Bennett, J.B., Gaynor, S.M. & Bindoff, N.L. 2010. Climate Futures for Tasmania: general climate impacts technical report. Antarctic Climate & Ecosystems Cooperative Research Centre, Hobart, Tasmania. climate futures for Tasmania, p.3.
Kyne, P.M., Heupel, M.R., White, W.T. and Simpfendorfer, C.A. 2021. The Action Plan for Australian Sharks and Rays 2021. National Environmental Science Program, Marine Biodiversity Hub, Hobart, Australia.
Last, P.R., Gledhill, D.C. & Sherman, C.S. 2016. Zearaja maugeana. The IUCN Red List of Threatened Species 2016: e.T64442A68650404. https://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T64442A68650404.en. Accessed on 06 January 2025
Macquarie Harbour Dissolved Oxygen Working Group. 2014. Final Report to the Tasmanian Salmonid Growers Association (TSFA). Published October, 2014. https://www.huonaqua.com.au/wp-content/uploads/2014/06/MHDOWG-ReportOctober-2014.pdf
Moreno, D., Patil, J., Deagle, B. and Semmens, J.M. 2022. Application of environmental DNA to survey Bathurst Harbour (Tasmania) for the Endangered Maugean skate (Zearaja maugeana). Report to the National Environmental Science Program. Institute of Marine and Antarctic Studies, University of Tasmania, Hobart.
Ross, J., Moreno, D., Bell, J., Mardones, J. and Beard, J. 2022. Assessment of the Macquarie Harbour Broadscale Environment Monitoring Program (BEMP) data from 2011 – 2020. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania. https://epa.tas.gov.au/documents/IMAS%20Assessment%20of%20Macquarie%20Harb our%20BEMP%20data%20from%202011%20to%202020%2c%20March%202022.pdf
Contributors: Janice Chanson, Re:wild
Stephanie Todd, Birdlife
Anna McCallum, Birdlife
Alistair Allan, Bob Brown Foundation
Dr Peter Kyne, Charles Darwin University
Dr Michael Grant, James Cook University
Dr Leonardo Guida, Australian Marine Conservation Society